In a radio communication system in compliance with the W-CDMA (Wideband-Code Division Multiple Access) scheme, various correspondences among a channel, a connection sequence and a radio physical channel are defined as described in non-patent document 1. As the correspondence between channels, three types of channels are defined as follows. First, a logical channel serves as a functional channel defined between an RLC and a MAC. Second, a transport channel serves as a functional channel defined between a MAC layer and a physical layer. Third, a physical channel serves as a functional channel in a physical layer. The logical channel has correspondence with the transport channel, and the transport channel has correspondence with the physical channel.
In a mobile communication system in compliance with the W-CDMA scheme, multiple logical channels are arranged (mapped) on multiple radio physical channels via multiple transport channels. FIG. 1 shows a conventional channel correspondence.
As illustrated in FIG. 2, on the other hand, user equipment (UE) is identified through an identifier (TMSI) in L3 (RRC) for a connection sequence prior to establishment of a RRC connection. Thus, since there is no individual correspondence with L2 until the RRC connection is established, a logical channel is transmitted in the CCCH. Also, since the UE is identified through the identifier in L2 (C- or H-RNTI) after establishment of the RRC connection, there is an individual correspondence in the L2 level, and the logical channel is modified to DCCH.
Specifically, a “RRC connection request” being a control signal at the establishment of the RRC connection is transmitted in the CCCH, and the radio physical channel is a PRACH (RACH). In addition, a “RRC connection setup” is transmitted in the CCCH, and the radio physical channel is a SCCPCH (FACH). Since the RRC connection has been established, in subsequent communications (signaling), the logical channel is transmitted in the DCCH and the radio physical channel is transmitted in the DPCH (DCCH). At the establishment of the RRC connection, the SDCCH is provided as a transmission path, and no channel is provided for transmission of U-plane.
In this fashion, a radio channel is modified by RRC signaling at the setup of the RRC connection (at the establishment of the RRC connection). A radio physical channel is set up for the U-plane transmission in a radio bearer setup. In other words, a channel is added by RRC signaling.
Also, the uplink access scheme uses a preamble prior to establishment of a dedicated channel. The preamble is 4,096 in chip length resulting from 256 repetitions of a 16 chip signature and is ramped in use. At receipt of the preamble, a base station (BTS) uses the AICH to return Acknowledgement (Ack) or Non-acknowledgement (Nack). In the case of Ack, data are transmitted over the PRACH after a predefined number of slots (conventionally three or four slots) in a system. The preamble includes no traffic information.
In the HSDPA (High Speed Downlink Packet Access) scheme, a shared channel (HS-PDSCH) for use between UEs is provided. In this channel, the logical channel such as DCCH or DTCH after the establishment of the RRC connection is transmitted. Concomitantly with HS-PDSCH, the HS-SCCH is provided to serve as a common control CH to report that data have arrived in the HS-PDSCH. In the HS-SCCH, UE recognizes based on data masked by the identifier for L2 that data destined for itself have arrived. Also, although each UE is capable of receiving the HS-SCCH up to four codes, HS-SCCH codes for use in the associated cell are reported to the UE by RRC signaling. The codes are included in radio bearer setup/reconfiguration. In HS-PDSCH, some techniques of HARQ and AMC are used.
For an enhanced uplink, since scheduling is carried out in a base station (Node B), a channel (E-DPCCH) for transmitting a reservation signal to transmit data to the base station (Node B) and a channel (E-RGCH, E-AGCH) for transmitting a reservation acknowledgement are defined. Furthermore, a channel (E-DPDCH) for transmitting uplink data is defined. In the E-DPDCH, HARQ is implemented similar to HS-PDSCH.
Non-patent document 1: “W-CDMA Mobile Communication Scheme (in Japanese)” edited by Keiji Tachikawa, pp. 103-157.